I'm not sure how shipping damage could have caused this problem, I would think it was more of a cable problem. Are you sure that no strands of cable were left in the internal guide after you pulled it out? In hindsight, if the cable was hard to pull out from the shifter end, then I would have chopped the cable at the shifter end and tried pulling it out at the derailleur end, this may have come out more smoothly and may not have left anything behind.
As to what you can do now, I would first try blasting air down the guide from both ends to see if you can dislodge any dirt or small items (hopefully there is a local bike shop with an air compressor that you can borrow for 2 minutes). Next is to try to shove something down there - if the wire hanger that was already suggested is too thick then an old spoke might be a better size (the best type would be something double-butted with a 1.5mm center section; cut off the threaded end, which is fatter, so you just have the thinner section). If that doesn't work then you've pretty much got to give up on the current guide, and I would then certainly look into the warranty option with Pinarello - the warranty should apply internationally and you shouldn't need to be in the country where you bought it. However, I'm really not sure if Pinarello will give you any assistance on this problem.
Your last resort is re-routing the cable, which won't be easy. First, you need to put a housing stop where the cable first enters the down tube, although you may be able to move the current one or get one that was made for another frame, so that shouldn't be too hard. Second, you'll need a guide to take the cable around the bottom bracket, which is going to be tough. You might want to make the cable exit the frame again before the BB, run a piece of external housing, then drill a new entry port with another housing stop, and make this so that the cable can go in a perfectly straight line from there, through the frame, and to the FD clamping bolt. If it was me, I wouldn't even bother going in and out of the downtube with the cable, and would run external housing all the way from the shifter to the BB, using three cable ties to strap the housing to the downtube. That is not going to look so pretty, but it would avoid having to drill two more holes.
Last edited by Chris_W on Tue Oct 30, 2012 10:35 pm, edited 1 time in total.